Bidirectional power converter

ABSTRACT

A bidirectional power converter circuit is controlled via a hysteresis loop such that the bidirectional power converter circuit can compensate in near real time for variations and even changes in transmit and receive coil locations without damaging components of the system. Because the bidirectional power converter is capable of both transmitting and receiving power (at different times), one circuit and board may be used as the main component in multiple wireless power converter designs.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority to, and hereby incorporates byreference in its entirety, U.S. Provisional Patent Application Ser. No.62/146,091 entitled “WIRELESS POWER SYSTEM” filed on Apr. 10, 2015.

A portion of the disclosure of this patent document contains materialthat is subject to copyright protection. The copyright owner has noobjection to the reproduction of the patent document or the patentdisclosure, as it appears in the U.S. Patent and Trademark Office patentfile or records, but otherwise reserves all copyright rights whatsoever.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

REFERENCE TO SEQUENCE LISTING OR COMPUTER PROGRAM LISTING APPENDIX

Not Applicable

BACKGROUND OF THE INVENTION

The present invention relates generally to power converters. Moreparticularly, this invention pertains to bidirectional power converters.

Designing circuits and laying out printed circuit boards is a timeconsuming and expensive process. Further, having multiple circuits andboards requires tracking multiple revisions of multiple circuits andprinted circuit boards, which adds layers of complexity. However, incurrent power transfer circuit design techniques, circuit and boardlayouts are created for one specific purpose. Having multiple circuitsand board layouts, each with multiple revisions is therefore heretoforeunavoidable.

Wireless charging systems are limited by, inter alia, size, space, andtransmitter/receiver orientation limitations. That is, wireless chargingsystems for batteries have wireless chargers, but the batteries directlyphysically contact the circuits of the device powered by the battery.The battery is not fully wireless which can be advantageous in wet orsterile environments. Further, wireless charging systems are currentlylimited by distance and/or orientation. That is, in some systems atransmitter coil must nearly be in contact with a receiver coil (e.g.,laying a cell phone equipped with wireless charging capabilities on awireless charging pad). In these systems, the Z directional differentialbetween the transmitter coil and the receiver coil is therefore nearzero while the X and Y directional variations are within a margin oferror (e.g., the cell phone and its power receiving coil are within aspecified diameter of a transmitting coil or antenna of the chargingpad). In other systems, the Z directional differential between thetransmitter coil and the receiver coil may be substantial, but thetransmitter coil and the receiver coil must be located on the same axis(i.e., almost no variation in the X and Y directions between the coilsand no variation in pitch). If the pitch or X-Y translation is notaccurate, the transmitter may be damaged, requiring replacement of thetransmitter circuit board. Thus, wireless charging systems that cannotcompensate for variations in transmitter and receiver coil relativelocations are difficult to manage and repair, and they are not practicalfor many uses in the field.

BRIEF SUMMARY OF THE INVENTION

Aspects of the present invention provide a bidirectional power convertercircuit. The bidirectional power converter circuit is capable of bothtransmitting and receiving power, such that the bidirectional powerconverter circuit of the present invention may be used as the maincomponent in multiple wireless power converter designs. Thebidirectional power converter circuit is controlled via a hysteresisloop such that the bidirectional power converter circuit can compensatein near real time for variations and even changes in transmitter andreceiver coil locations without damaging any components of the system.

In one aspect, the bidirectional power converter of the presentinvention is operable to provide an alternating current (AC) power to anAC terminal of the bidirectional power converter in a transmit mode ofthe bidirectional power converter and provide direct current (DC) powerat a DC output terminal of the bidirectional power converter in areceive mode of the bidirectional power converter. The bidirectionalpower converter includes an oscillator, an amplifier, a modulator, ahysteretic receiver circuit, a transmit relay, a rectifier, a receiverelay, and a hysteretic control circuit. The oscillator is configured toprovide a drive signal at a base frequency when the bidirectional powerconverter is operating in the transmit mode. The amplifier is configuredto receive power from a power source via a DC input terminal of thebidirectional power converter and provide an AC output signal to the ACterminal of the bidirectional power converter in response to receivingthe drive signal when the bidirectional power converter is operating inthe transmit mode. The modulator is configured to selectively providethe drive signal from the oscillator to the amplifier as a function of ahysteretic control signal when the bidirectional power converter isoperating in the transmit mode. The hysteretic receiver circuit isconfigured to receive a transmitted control signal at the bidirectionalpower converter and provide the hysteretic control signal to themodulator as a function of the received, transmitted control signal whenthe bidirectional power converter is operating in the transmit mode. Thetransmit relay is configured to electrically connect the amplifier tothe AC terminal of the bidirectional power converter when thebidirectional power converter is operating in the transmit mode andelectrically disconnect the amplifier from the AC terminal of thebidirectional power converter when the bidirectional power converter isoperating in the receive mode. The rectifier is configured to receive analternating current power signal from the AC terminal of thebidirectional power converter and provide a DC output to the DC outputterminal of the bidirectional power converter when the bidirectionalpower converter is operating in the receive mode. A receive relay isconfigured to enable the rectifier to provide DC output to the DC outputterminal of the bidirectional power converter when the bidirectionalpower converter is operating in the receive mode and prevent therectifier from providing the DC output to the DC output terminal whenthe bidirectional power converter is operating in the transmit mode. Thehysteretic control circuit is configured to monitor the DC output andtransmit the control signal as a function of the monitored DC outputwhen the bidirectional power converter is operating in the receive mode.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a block diagram of how FIGS. 1A to 1I fit together to form ablock diagram of one embodiment of a bidirectional power converter.

FIG. 1A is a partial block diagram of the block diagram of thebidirectional power converter of FIG. 1.

FIG. 1B is a partial block diagram of the block diagram of thebidirectional power converter of FIG. 1.

FIG. 1C is a partial block diagram of the block of diagram of thebidirectional power converter of FIG. 1.

FIG. 1D is a partial block diagram of the block of diagram of thebidirectional power converter of FIG. 1.

FIG. 1E is a partial block diagram of the block of diagram of thebidirectional power converter of FIG. 1.

FIG. 1F is a partial block diagram of the block of diagram of thebidirectional power converter of FIG. 1.

FIG. 1G is a partial block diagram of the block of diagram of thebidirectional power converter of FIG. 1.

FIG. 1H is a partial block diagram of the block of diagram of thebidirectional power converter of FIG. 1.

FIG. 1I is a partial block diagram of the block of diagram of thebidirectional power converter of FIG. 1.

FIG. 2 is a block diagram of how FIG. 2A to FIG. 2P fit together to forma partial schematic diagram of the bidirectional power converter of FIG.1.

FIG. 2A is a partial schematic diagram of the bidirectional powerconverter of FIG. 2.

FIG. 2B is a partial schematic diagram of the bidirectional powerconverter of FIG. 2.

FIG. 2C is a partial schematic diagram of the bidirectional powerconverter of FIG. 2.

FIG. 2D is a partial schematic diagram of the bidirectional powerconverter of FIG. 2.

FIG. 2E is a partial schematic diagram of the bidirectional powerconverter of FIG. 2.

FIG. 2F is a partial schematic diagram of the bidirectional powerconverter of FIG. 2.

FIG. 2G is a partial schematic diagram of the bidirectional powerconverter of FIG. 2.

FIG. 2H is a partial schematic diagram of the bidirectional powerconverter of FIG. 2.

FIG. 2I is a partial schematic diagram of the bidirectional powerconverter of FIG. 2.

FIG. 2J is a partial schematic diagram of the bidirectional powerconverter of FIG. 2.

FIG. 2K is a partial schematic diagram of the bidirectional powerconverter of FIG. 2.

FIG. 2L is a partial schematic diagram of the bidirectional powerconverter of FIG. 2.

FIG. 2M is a partial schematic diagram of the bidirectional powerconverter of FIG. 2.

FIG. 2N is a partial schematic diagram of the bidirectional powerconverter of FIG. 2.

FIG. 2O is a partial schematic diagram of the bidirectional powerconverter of FIG. 2.

FIG. 2P is a partial schematic diagram of the bidirectional powerconverter of FIG. 2.

FIG. 3 is a block diagram of how FIGS. 3A to 3V fit together to form apartial schematic diagram of the bidirectional power converter of FIGS.1 and 2.

FIG. 3A is a partial schematic diagram of the bidirectional powerconverter of FIG. 3.

FIG. 3B is a partial schematic diagram of the bidirectional powerconverter of FIG. 3.

FIG. 3C is a partial schematic diagram of the bidirectional powerconverter of FIG. 3.

FIG. 3D is a partial schematic diagram of the bidirectional powerconverter of FIG. 3.

FIG. 3E is a partial schematic diagram of the bidirectional powerconverter of FIG. 3.

FIG. 3F is a partial schematic diagram of the bidirectional powerconverter of FIG. 3.

FIG. 3G is a partial schematic diagram of the bidirectional powerconverter of FIG. 3.

FIG. 3H is a partial schematic diagram of the bidirectional powerconverter of FIG. 3.

FIG. 3I is a partial schematic diagram of the bidirectional powerconverter of FIG. 3.

FIG. 3J is a partial schematic diagram of the bidirectional powerconverter of FIG. 3.

FIG. 3K is a partial schematic diagram of the bidirectional powerconverter of FIG. 3.

FIG. 3L is a partial schematic diagram of the bidirectional powerconverter of FIG. 3.

FIG. 3M is a partial schematic diagram of the bidirectional powerconverter of FIG. 3.

FIG. 3N is a partial schematic diagram of the bidirectional powerconverter of FIG. 3.

FIG. 3O is a partial schematic diagram of the bidirectional powerconverter of FIG. 3.

FIG. 3P is a partial schematic diagram of the bidirectional powerconverter of FIG. 3.

FIG. 3Q is a partial schematic diagram of the bidirectional powerconverter of FIG. 3.

FIG. 3R is a partial schematic diagram of the bidirectional powerconverter of FIG. 3.

FIG. 3S is a partial schematic diagram of the bidirectional powerconverter of FIG. 3.

FIG. 3T is a partial schematic diagram of the bidirectional powerconverter of FIG. 3.

FIG. 3U is a partial schematic diagram of the bidirectional powerconverter of FIG. 3.

FIG. 3V is a partial schematic diagram of the bidirectional powerconverter of FIG. 3.

FIG. 4 is a block diagram of how FIGS. 4A to 4Z fit together to form apartial schematic diagram of the bidirectional power converter of FIGS.1, 2, and 3.

FIG. 4A is a partial schematic diagram of the bidirectional powerconverter of FIG. 4.

FIG. 4B is a partial schematic diagram of the bidirectional powerconverter of FIG. 4.

FIG. 4C is a partial schematic diagram of the bidirectional powerconverter of FIG. 4.

FIG. 4D is a partial schematic diagram of the bidirectional powerconverter of FIG. 4.

FIG. 4E is a partial schematic diagram of the bidirectional powerconverter of FIG. 4.

FIG. 4F is a partial schematic diagram of the bidirectional powerconverter of FIG. 4.

FIG. 4G is a partial schematic diagram of the bidirectional powerconverter of FIG. 4.

FIG. 4H is a partial schematic diagram of the bidirectional powerconverter of FIG. 4.

FIG. 4I is a partial schematic diagram of the bidirectional powerconverter of FIG. 4.

FIG. 4J is a partial schematic diagram of the bidirectional powerconverter of FIG. 4.

FIG. 4K is a partial schematic diagram of the bidirectional powerconverter of FIG. 4.

FIG. 4L is a partial schematic diagram of the bidirectional powerconverter of FIG. 4.

FIG. 4M is a partial schematic diagram of the bidirectional powerconverter of FIG. 4.

FIG. 4N is a partial schematic diagram of the bidirectional powerconverter of FIG. 4.

FIG. 4O is a partial schematic diagram of the bidirectional powerconverter of FIG. 4.

FIG. 4P is a partial schematic diagram of the bidirectional powerconverter of FIG. 4.

FIG. 4Q is a partial schematic diagram of the bidirectional powerconverter of FIG. 4.

FIG. 4R is a partial schematic diagram of the bidirectional powerconverter of FIG. 4.

FIG. 4S is a partial schematic diagram of the bidirectional powerconverter of FIG. 4.

FIG. 4T is a partial schematic diagram of the bidirectional powerconverter of FIG. 4.

FIG. 4U is a partial schematic diagram of the bidirectional powerconverter of FIG. 4.

FIG. 4V is a partial schematic diagram of the bidirectional powerconverter of FIG. 4.

FIG. 4W is a partial schematic diagram of the bidirectional powerconverter of FIG. 4.

FIG. 4X is a partial schematic diagram of the bidirectional powerconverter of FIG. 4.

FIG. 4Y is a partial schematic diagram of the bidirectional powerconverter of FIG. 4.

FIG. 4Z is a partial schematic diagram of the bidirectional powerconverter of FIG. 4.

FIG. 5 is a block diagram of how FIG. 5A to FIG. 5J fit together to forma partial schematic diagram of the bidirectional power converter ofFIGS. 1-4.

FIG. 5A is a partial schematic diagram of the bidirectional powerconverter of FIG. 5.

FIG. 5B is a partial schematic diagram of the bidirectional powerconverter of FIG. 5.

FIG. 5C is a partial schematic diagram of the bidirectional powerconverter of FIG. 5.

FIG. 5D is a partial schematic diagram of the bidirectional powerconverter of FIG. 5.

FIG. 5E is a partial schematic diagram of the bidirectional powerconverter of FIG. 5.

FIG. 5F is a partial schematic diagram of the bidirectional powerconverter of FIG. 5.

FIG. 5G is a partial schematic diagram of the bidirectional powerconverter of FIG. 5.

FIG. 5H is a partial schematic diagram of the bidirectional powerconverter of FIG. 5.

FIG. 5I is a partial schematic diagram of the bidirectional powerconverter of FIG. 5.

FIG. 5J is a partial schematic diagram of the bidirectional powerconverter of FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

While the making and using of various embodiments of the presentinvention are discussed in detail below, it should be appreciated thatthe present invention provides many applicable inventive concepts thatcan be embodied in a wide variety of specific contexts. The specificembodiments discussed herein are merely illustrative of specific ways tomake and use the invention and do not delimit the scope of theinvention.

To facilitate the understanding of the embodiments described herein, anumber of terms are defined below. The terms defined herein havemeanings as commonly understood by a person of ordinary skill in theareas relevant to the present invention. Terms such as “a,” “an,” and“the” are not intended to refer to only a singular entity, but ratherinclude the general class of which a specific example may be used forillustration. The terminology herein is used to describe specificembodiments of the invention, but their usage does not delimit theinvention, except as set forth in the claims.

The phrase “in one embodiment,” as used herein does not necessarilyrefer to the same embodiment, although it may. Conditional language usedherein, such as, among others, “can,” “might,” “may,” “e.g.,” and thelike, unless specifically stated otherwise, or otherwise understoodwithin the context as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements and/or states. Thus, such conditional language is notgenerally intended to imply that features, elements and/or states are inany way required for one or more embodiments or that one or moreembodiments necessarily include logic for deciding, with or withoutauthor input or prompting, whether these features, elements and/orstates are included or are to be performed in any particular embodiment.

The terms “coupled” and “connected” mean at least either a directelectrical connection between the connected items or an indirectconnection through one or more passive or active intermediary devices.

The term “circuit” means at least either a single component or amultiplicity of components, either active and/or passive, that arecoupled together to provide a desired function.

The terms “switching element” and “switch” may be used interchangeablyand may refer herein to at least: a variety of transistors as known inthe art (including but not limited to FET, BJT, IGBT, JFET, etc.), aswitching diode, a silicon controlled rectifier (SCR), a diode foralternating current (DIAC), a triode for alternating current (TRIAC), amechanical single pole/double pole switch (SPDT), or electrical, solidstate or reed relays. Where either a field effect transistor (FET) or abipolar junction transistor (BJT) may be employed as an embodiment of atransistor, the scope of the terms “gate,” “drain,” and “source”includes “base,” “collector,” and “emitter,” respectively, andvice-versa.

The terms “power converter” and “converter” unless otherwise definedwith respect to a particular element may be used interchangeably hereinand with reference to at least DC-DC, DC-AC, AC-DC, buck, buck-boost,boost, half-bridge, full-bridge, H-bridge or various other forms ofpower conversion or inversion as known to one of skill in the art.

As used herein, “micro” refers generally to any semiconductor basedmicroelectronic circuit including, but not limited to, a comparator, anoperational amplifier, a microprocessor, a timer, an AND gate, a NORgate, an OR gate, an XOR gate, or a NAND gate.

Terms such as “providing,” “processing,” “supplying,” “determining,”“calculating” or the like may refer at least to an action of a computersystem, computer program, signal processor, logic or alternative analogor digital electronic device that may be transformative of signalsrepresented as physical quantities, whether automatically or manuallyinitiated.

To the extent the claims recited herein recite forms of signaltransmission, those forms of signal transmission do not encompasstransitory forms of signal transmission.

Referring now to FIGS. 1-5, in one embodiment, a bidirectional powerconverter 100 is operable to provide AC power to an AC terminal 102 ofthe bidirectional power converter 100 in a transmit mode of thebidirectional power converter 100. The bidirectional power converter 100is further operable to provide DC power at a DC output terminal 104 ofthe bidirectional power converter 100 in a receive mode of thebidirectional power converter 100. In one embodiment, bidirectionalpower converter 100 includes an oscillator 106, an amplifier 108, amodulator 110, a hysteretic receiver circuit 112, a transmit relay 114,a rectifier 116 a receive relay 118, and a hysteretic control circuit120. In one embodiment, the bidirectional power converter 100 includestwo generally independent sections, a transmitter section and a receiversection. The transmitter section and the receiver section areselectively connected to the DC output terminal 104 and AC terminal 102by a set of solid state relays (e.g., transmit relay 114 and receiverelay 118).

The oscillator 106 is configured to provide a drive signal at a basefrequency when the bidirectional power converter 100 is operating in thetransmit mode. In one embodiment, the base frequency of the oscillator106 is approximately 100 kHz. In one embodiment, the oscillator 106generates the carrier frequency at which power is transmitted by thebidirectional power converter transmitter section. In one embodiment,micro U17 of oscillator 106 is an industry standard 556 timer whichcontains two 555 timers. One timer of micro U17 is configured as a oneshot timer, and the other timer is a free running oscillator,oscillating at 100 KHz. The one shot timer of micro U17 guarantees a 50%duty cycle for the modulator 110 during startup of the transmittersection. Resistors R65 and R70 as well as capacitors C47 and C49 set thefree running frequency of 100 kHz (or some other base frequency).Resistors R67 and R68 and capacitor C44 set the one shot timer for aprecise 50% duty cycle out of pin 9 of the micro U17.

The amplifier 108 is configured to receive power from a power source viaDC input terminal 122 of the bidirectional power converter 100 andprovide an AC output signal to the AC terminal 102 of the bidirectionalpower converter 100 in response to receiving the drive signal when thebidirectional power converter 100 is operating in the transmit mode. Inone embodiment, the amplifier 108 is a full bridge amplifier. In oneembodiment, the amplifier 108 provides a differential output capable ofup to 500 W RMS. Power MOSFETS Q1/Q4 and Q5/Q6 (see FIG. 2) are drivenby a first micro U1 to form a first half bridge power amplifier HBPA1,and power MOSFETS Q9/Q12 and Q13/Q14 are driven by a second micro U10 toform a second half bridge power amplifier HBPA2. The outputs of thefirst half bridge power amplifier HBPA1 and the second half bridge poweramplifier HBPA2 combine at the load (i.e., at the AC output 102) at 180degrees out of phase to provide power drive at the load. Micros U1 andU10 provide fast turn on/off drive to their respective power MOSFETS toassure efficient switching operation. Micros U1 and U10 also providegalvanic isolation electrically isolating the input/output grounds.Micros U3 and U4 cooperate to provide dead-time control for powerMOSFETS Q1/Q4 and Q5/Q6 assuring that they are never on at the same timecausing a dead short for the power supply +PWR_TX. Micros U11 and U12provide the same functionality as micros U3 and U4 for Q9/Q12 andQ13/Q14. Micros U2, U9, U5, and U33 convert the four inputs to the fullbridge amplifier to the necessary drive to derive a differential ACoutput voltage at the load (i.e., AC output terminal 102). This part ofthe amplifier ensures that the output of each HBPA in the disable stateis ground, essentially keeping power MOSFETS Q5/Q6 for the first halfbridge power amplifier HBPA1 and power MOSFETS Q13/Q14 for the secondhalf bridge power amplifier HBPA2 in the on state.

The modulator 110 is configured to selectively provide the drive signalfrom the oscillator 106 to the amplifier 108 as a function of ahysteretic control signal when the bidirectional power converter 100 isoperating in the transmit mode. In one embodiment, the modulator 110 isan amplitude shift keyed modulator. The Amplitude Shift Keying Modulator110 provides a digitized version of AM (Amplitude Modulation) to thefull bridge amplifier 108, effectively keying on/off the full bridgeamplifier 108 dependent on the logic state of the feedback signal (i.e.,hysteresis control signal) received from a second bidirectional powerconverter configured as a receiver (i.e., in the receive mode). The AMOD110 effect is to keep the voltage generated at the DC output terminal ofthe second bidirectional power converter assembly output constant. TheAMOD 110 accepts four inputs FD_BCK (i.e., hysteretic control signal),100 KHz_OSC (i.e., drive signal) from the oscillator 106, ONE_SHOT(i.e., one shot signal) from the one shot timer 170, and SSL (i.e., thepulse width modulated signal) from the slow start logic circuit 172. TheAMOD 110 generates four outputs (i.e., two sets of differential outputs)to the full bridge amplifier 108: 100 KHz_OUT_MODULATED, 100KHz_OUT_MODULATED_N, TX_EN, TX_EN_N. The modulator enable signal(MODULATOR_EN) enables/disables the AMOD (modulator) 110. Once the AMOD110 is enabled, the drive signal from the oscillator 106 (100 KHz_OSC)drives CLK pins of micro U15 and micro U38, sequentially clocking thelogic state of the hysteresis control signal (FD_BCK), once the one shotsignal (ONE_SHOT) has settled to a logic 0 and the slow start circuit172 pulse width modulated signal (SSL) has settled to a logic 1. Amodulator internal signal 100 KHz_OUT_MODULATED is derived from microU38 and its inverted version from micro U35. The TX_EN and TX_EN_Nsignals are derived from the Q/Q_N pins of U15B. These outputs drive thefull bridge amplifier 108 and contain the feedback information from thesecond bidirectional power converter 100 configured as a receiver. Alogic 1 at D of micro U15A turns on the full bridge amplifier 108continuously while a logic 0 at D of micro U15A turns off the fullbridge amplifier 108 and turns on power MOSFETS Q5, Q6, Q13, and Q14 tokeep each half bridge power amplifier (i.e., HBPA1 and HBPA2) output atground potential.

The hysteretic receiver circuit 112 is configured to receive atransmitted control signal at the bidirectional power converter 100 andprovide the hysteretic control signal to the modulator 110 as a functionof the received, transmitted control signal when the bidirectional powerconverter 100 is operating in the transmit mode.

The transmit relay 114 is configured to electrically connect theamplifier 108 to the AC terminal 102 of the bidirectional powerconverter 100 when the bidirectional power converter 100 is operating inthe transmit mode and electrically disconnect the amplifier 108 from theAC terminal 102 of the bidirectional power converter 100 when thebidirectional power converter 100 is operating in the receive mode.

The rectifier 116 is configured to receive an alternating current powersignal from the AC terminal 102 of the bidirectional power converter 100and provide a DC output to the DC output terminal 104 of thebidirectional power converter 100 when the bidirectional power converter100 is operating in the receive mode. In one embodiment, the rectifier116 is a full wave rectifier. The rectifier 116 converts the AC powerreceived to pulsating DC at twice the incoming frequency. The rectifier116 is capable of receiving up to a maximum of 500 W RMS. The rectifieris implemented via diodes D14 through D19 and D22 through D27 (see FIG.4) connected in a full bridge rectifier configuration. A parallel diodecombination allows for higher power while keeping the efficiency high.In one embodiment, the diodes D14 through D19 and D22 through D27 are ofthe Schottky type for high speed operation.

The receive relay 118 is configured to enable the rectifier 116 toprovide the DC output to the DC output terminal 104 of the bidirectionalpower converter 100 when the bidirectional power converter 100 isoperating in the receive mode and prevent the rectifier 116 fromproviding the DC output to the DC output terminal 104 when thebidirectional power converter 100 is operating the transmit mode. In oneembodiment, the receive relay 118 is configured to enable the rectifier116 to provide the DC output to the DC output terminal 104 when thebidirectional power converter 100 is operating in the receive mode byelectrically connecting the rectifier 116 to the DC output terminal 104of the bidirectional power converter 100 when the bidirectional powerconverter 100 is operating in the receive mode. The receive relay 118 isfurther configured to prevent the rectifier 116 from providing the DCoutput to the DC output terminal 104 when the bidirectional powerconverter 100 is operating in the transmit mode by electricallydisconnecting the rectifier 116 from the AC terminal 102 of thebidirectional power converter 100 when the bidirectional power converter100 is operating in the transmit mode. In another embodiment, thereceive relay 118 is configured to prevent the rectifier 116 fromproviding the DC output to the DC output terminal 104 when thebidirectional power converter 100 is operating in the transmit mode byelectrically disconnecting the rectifier 116 from the DC output terminal104.

The hysteretic control circuit 120 is configured to monitor the DCoutput and transmit a control signal as a function of the monitored DCoutput when the bidirectional power converter 100 is operating in thereceive mode. In one embodiment, the hysteretic control circuit 120includes a hysteretic controller 132 and a transmitter. The hystereticcontroller 132 is configured to provide a logic signal. The logic signalis a 1st binary value when a voltage of the DC output from the rectifier116 is less than a predetermined threshold, and the logic signal is a2nd binary value when the voltage of the DC output is more than thepredetermined threshold. The 1st binary value is different than the 2ndbinary value. The response time of the hysteretic controller 132 isalmost instantaneous which gives the system (i.e., a pair ofbidirectional power converters 100, one operating in the transmit modeand one operating in the receive mode) excellent transient response atthe DC output terminal. The only delays involved in the control loop arethe propagation delays of the transmitter and hysteretic receivercircuit 112 and other system blocks of the power network (i.e.,modulator 116 and amplifier 108) which are very short. Another benefitof the hysteretic controller 132 and hysteretic receiver circuit 112 isthat the system has an unconditional operation stability, requiring nofeedback compensating components for stable operation. In oneembodiment, the hysteretic controller 132 further includes a feedbacknetwork. The feedback network provides a reduced voltage representativeof the DC output voltage of the rectifier 116, allowing for the outputof the bidirectional power converter to be adjusted anywhere between 12and 24 V DC as a function of the feedback network components (i.e.,resistors). Resistors R92, R95, and R101 (see FIG. 4) and capacitor C89provide the feedback network function. Resistors R92, R95, and R101 forma voltage divider that divides down the output voltage (i.e., the DCoutput voltage from the rectifier 116 and DC filter 186) to equal areference voltage applied to the hysteretic controller 132 by the linearregulator 182. At any time the output is regulated between 12-24V, thevoltage generated across R101 is always 2.5V which is equal to thereference voltage of micro U23A provided by the linear regulator 182.Capacitor C89 is used to pass some of the ripple of the DC output signalfrom the rectifier 116 and DC filter 186 to the input of the micro U23Ato speed up the switching action of the hysteretic controller 132,increasing efficiency and stability of the bidirectional powerconverter. In a 1st embodiment of the hysteretic controller 132, thetransmitter is a coil pulse driver 140 configured to receive the logicsignal and generate a magnetic field via a magnetic coupling coil. Thegenerated magnetic field is indicative of the logic signal. In the 1stembodiment, the hysteretic receiver circuit 112 includes a magneticsensor configured to receive a magnetic field and provide hystereticcontrol signal to the modulator 110 as a function of the receivedmagnetic field. In one version, a linear hall-effect sensor connects tojumper J3 of the bidirectional power converter 100. Micro U6A isconfigured as an AC coupled first-order low pass filter, for removingsome noise picked up by the hall-effect sensor. Micro U6B and comparatorU41A form a comparator circuit with a threshold set by micro U6B. Whenthe output of micro U6A equals the threshold set by micro U6B,comparator U41A sets its output (i.e., the hysteresis control signal) toa logic 1, and the comparator U41A sets its output (i.e., the hysteresiscontrol signal) to a logic zero when the output of micro U6A is lessthan the threshold set by micro U6B. In a 2nd embodiment, thetransmitter is a radio frequency (RF) transmitter configured to receivethe logic signal and transmit an RF signal via and antenna, wherein thetransmitted RF signal is indicative of the logic signal. In the 2ndembodiment, hysteretic receiver circuit 112 includes an RF receiverconfigured to receive an RF signal and provide the hysteretic controlsignal to the modulator 110 as a function of the received RF signal. Ina 3rd embodiment, the transmitter is an optical transmitter 142configured to receive the logic signal and transmit an optical signalvia an infrared emitter, wherein the transmitted optical signal isindicative of the logic signal. In the 3rd embodiment, the hystereticreceiver circuit 112 includes an infrared receiver 144 configured toreceive an optical signal and provide the hysteretic control signal tothe modulator 110 as a function of the received optical signal.

In one embodiment, the bidirectional power converter 100 furtherincludes a direction control input 130 configured to receive a directioncontrol signal. The direction control signal is provided to the transmitrelay 114 and the receive relay 118 to set the bidirectional powerconverter 100 in either the transmit mode or the receive mode.

In one embodiment, the bidirectional power converter 100 furtherincludes a coil 150 connected to the AC terminal 102 of thebidirectional power converter 100. The coil 150 is configured to receivethe AC output signal from the amplifier 108 and emit a correspondingelectromagnetic field when the bidirectional power converter 100 isoperating in the transmit mode. The coil 150 is further operable toconvert electromagnetic flux into an AC power signal when thebidirectional power converter 100 is operating in the receive mode. Inone embodiment, the coil 150 includes a wire coil 152 and a tuningcapacitor 154. The tuning capacitor 154 connects the wire coil 152 tothe AC terminal 102 of the bidirectional power converter 100.

In one embodiment, the bidirectional power converter 100 furtherincludes a DC charge control relay 160 (which can be external to othercomponents) including a unified DC terminal 162. The DC control relay160 is configured to connect to the DC input terminal 122 and the DCoutput terminal 104. The DC charge control relay 160 is configured toelectrically isolate the DC input terminal 122 from the DC outputterminal 104. The DC charge control relay 160 further electricallyconnects the DC input terminal 122 to the unified DC terminal 162 whenthe bidirectional power converter 100 is operating in the transmit modeand electrically connects the DC output terminal 104 to the unified DCterminal 162 when the bidirectional power converter 100 is operating inthe receive mode.

In one embodiment, bidirectional converter 100 further includes a slowstart circuit 172 and a one-shot timer 170. The slow start circuit 172is configured to provide a pulse width modulated signal that increasesfrom 0 to 100% duty cycle (i.e., “on” time) beginning when thebidirectional power converter 100 begins operating in the transmit mode.The rate of increase of the duty cycle of the pulse width modulatedsignal is generally linear. The effect of the pulse width modulatedsignal (SSL) from the slow start circuit 172 is to control the amount oftime the amplifier 108 remains in the on-state. This function is onlyused initially when the bidirectional power converter 100 is enabled totransmit for the first time (i.e., at each startup of the bidirectionalpower converter 100 as a transmitter). The pulse width modulated signal(SSL) varies the on-time of the amplifier 108 from 0 (fully off) to 1(fully on continuously) by controlling the on-time at the modulator 110,effectively ramping up the voltage received at a second bidirectionalpower converter 100 configured as a receiver until a set regulatedvoltage (i.e., a target output voltage) is reached. Once the set voltageis reached, the output of the SSL remains at a logic 1. In oneembodiment, of the slow start circuit 172, micro U16B is configured as asaw-tooth oscillator. The output of micro U16B, taken across capacitorsC41 and C42, is fed to PWM comparator U16A. A linear DC voltage isgenerated across a capacitor bank (i.e., capacitors C35, C36, C37, C38,and C39) by feeding the capacitor bank a constant current generated byswitch Q18. This linear generated DC voltage is compared in PWMcomparator U16A to the saw-tooth like ramp voltage generated by microU16B and a pulse width modulated signal is generated by PWM comparatorU16A to provide to the modulator 110.

The one-shot timer 170 is configured to provide a one-shot signal to themodulator 110 (and the one shot signal is “on”) when the bidirectionalpower converter 100 begins operating in the transmit mode and for apredetermined period of time thereafter. Modulator 110 is furtherconfigured to provide the drive signal from the oscillator 106 toamplifier 108 when the pulse width modulated signal is on and at leastone of the hysteretic control signal and one-shot signal are “on.” Inone embodiment, the one shot timer 170 provides a precise timecontrolled “momentary-on” enable signal to the AMOD (i.e., modulator110) when the transmitter section is first enabled. If, in the timeframe generated by the one shot timer 170, a feedback signal (i.e.,hysteresis control signal) is not received by the bidirectional powerconverter 100, the one shot timer 170 terminates the transmission. Thatis, the modulator 110 ceases providing the drive signal from theoscillator 106 to the amplifier 108 because the modulator 110 isreceiving neither the hysteresis control signal nor the one shot signal.In addition, this embodiment permits the transmit section to terminateoperation in the event the feedback signal is interrupted, once it hasbeen received. Micro U42 (see FIG. 3) is the one shot timer 170 designedutilizing a standard 555 timer. The on-time of the one shot signal iscontrolled by resistor R146 and capacitors C133 and C134. The modulatorenable signal (MODULATOR_EN) provided by the control logic 176 triggersthe one shot timer 170 via pin 2 of micro U42 (i.e., 555 timer) throughswitch Q37.

In one embodiment, the bidirectional power converter 100 furtherincludes a temperature sensor 174 and control logic 176. The temperaturesensor 174 is configured to monitor a temperature of the amplifier 108and provide a temperature sensing signal indicative of the monitoredtemperature. The control logic 176 is configured to provide a modulatorenable signal to the modulator 110 as a function of the temperaturesensing signal and the direction signal such that the modulator enablesignal is provided when the direction control signal sets thebidirectional power converter 100 in the transmit mode and thetemperature sensing signal is indicative of a temperature less than apredetermined temperature. The modulator 110 does not provide the drivesignal from the oscillator 106 to the amplifier 108 when the modulator110 is not receiving a modulator enable signal. In one embodiment, thetemperature sensor 174 monitors the full bridge amplifier 108 viathermal coupling of the temperature sensor 174 to the full bridgeamplifier 108. When the temperature at the full bridge amplifier 108reaches a threshold set by the temperature sensor 174, the temperaturesensor 174 sets its output disabling the full bridge amplifier 108 viathe modulator 110. When the temperature at the full bridge amplifier 108drops to a safe value, the temperature sensor 174 re-enables the fullbridge amplifier 108 via the modulator 110. The status of thetemperature sensor 174 can be obtained from the signal connector atpin-6. In one embodiment, micro U14 is an integrated circuitmanufactured by Maxim Integrated™ capable of +/−0.5 degree C. accuracyand a temperature range of −20 to 100 degree C. Resistors R51, R53, andR53 and switch Q17 set the two set points for micro U14. In oneembodiment, the set points disable at 80 C and enable at 40 C. In oneembodiment of the control logic 176, the control logic 176 takes in thesignals from the temperature sensor 174 (TEMP_EN_DIS) and the TX_ONsignal from signal connector pin-2 and generates a single enable/disablesignal (MODULATOR_EN) for the modulator 110. Micros U39 and U40 providethe logic function needed for the control logic 176. When the outputfrom the temperature sensor 174 (TEMP_EN_DIS) is logic 0 and transmitterenable signal from pin 2 of the signal connector (TRANS_EN) is logic 1,modulator enable signal (MODULATOR_EN) is a logic 1, enabling thetransmit function of the bidirectional power converter 100.

In one embodiment, the bidirectional power converter 100 furtherincludes a switching regulator 180. The switching regulator 180 isconfigured to generate bias voltages when the bidirectional powerconverter 100 is receiving power from the power source at the DC inputterminal 122 of the bidirectional power converter 100. Switchingregulator 180 provides at least one of the generated bias voltages tothe oscillator 106, the amplifier 108, the modulator 110, the hystereticreceiver circuit 112, and the transmit relay 114, the slow start circuit172, the one-shot timer 170, and the temperature sensor 174. In oneembodiment, the switching regulator 180 implements a buck switching typeregulator.

In one embodiment, the bidirectional power converter 100 furtherincludes a linear regulator 182. The linear regulator 182 is configuredto receive the DC output from the rectifier 116 and provide biasvoltages to the hysteretic control circuit 120 when the bidirectionalpower converter 100 is operating in the receive mode.

In one embodiment, the bidirectional power converter 100 furtherincludes a DC filter 186 configured to relay the DC output provided bythe rectifier 116 to the DC output terminal 104. The DC filter 186converts the pulsating DC output from the rectifier 116 to a fixed DCvoltage with relatively low ripple. Capacitor bank C76 through C80charge to the peak value of the rectified AC voltage (i.e., thepulsating DC output provided by the rectifier 116) and supply power tothe load (i.e., the DC output terminal) during certain times (i.e., thetroughs) of the pulsating DC output signal provided by the rectifier116.

In one embodiment, the bidirectional power converter 100 furtherincludes a plurality of isolators 190. The plurality of isolators 190are configured to isolate the DC input terminal 122 from the AC terminal102 and the AC terminal 102 from the DC output terminal 104 of thebidirectional power converter 100 such that the bidirectional powerconverter 100 is an isolated power source in both the transmit mode andthe receive mode.

It will be understood by those of skill in the art that information andsignals may be represented using any of a variety of differenttechnologies and techniques (e.g., data, instructions, commands,information, signals, bits, symbols, and chips may be represented byvoltages, currents, electromagnetic waves, magnetic fields or particles,optical fields or particles, or any combination thereof). Likewise, thevarious illustrative logical blocks, modules, circuits, and algorithmsteps described herein may be implemented as electronic hardware,computer software, or combinations of both, depending on the applicationand functionality. Moreover, the various logical blocks, modules, andcircuits described herein may be implemented or performed with a generalpurpose processor (e.g., microprocessor, conventional processor,controller, microcontroller, state machine or combination of computingdevices), a digital signal processor (“DSP”), an application specificintegrated circuit (“ASIC”), a field programmable gate array (“FPGA”) orother programmable logic device, discrete gate or transistor logic,discrete hardware components, or any combination thereof designed toperform the functions described herein. Similarly, steps of a method orprocess described herein may be embodied directly in hardware, in asoftware module executed by a processor, or in a combination of the two.A software module may reside in RAM memory, flash memory, ROM memory,EPROM memory, EEPROM memory, registers, hard disk, a removable disk, aCD-ROM, or any other form of storage medium known in the art. Althoughembodiments of the present invention have been described in detail, itwill be understood by those skilled in the art that variousmodifications can be made therein without departing from the spirit andscope of the invention as set forth in the appended claims.

A controller, processor, computing device, client computing device orcomputer, such as described herein, includes at least one or moreprocessors or processing units and a system memory. The controller mayalso include at least some form of computer readable media. By way ofexample and not limitation, computer readable media may include computerstorage media and communication media. Computer readable storage mediamay include volatile and nonvolatile, removable and non-removable mediaimplemented in any method or technology that enables storage ofinformation, such as computer readable instructions, data structures,program modules, or other data. Communication media may embody computerreadable instructions, data structures, program modules, or other datain a modulated data signal such as a carrier wave or other transportmechanism and include any information delivery media. Those skilled inthe art should be familiar with the modulated data signal, which has oneor more of its characteristics set or changed in such a manner as toencode information in the signal. Combinations of any of the above arealso included within the scope of computer readable media. As usedherein, server is not intended to refer to a single computer orcomputing device. In implementation, a server will generally include anedge server, a plurality of data servers, a storage database (e.g., alarge scale RAID array), and various networking components. It iscontemplated that these devices or functions may also be implemented invirtual machines and spread across multiple physical computing devices.

This written description uses examples to disclose the invention andalso to enable any person skilled in the art to practice the invention,including making and using any devices or systems and performing anyincorporated methods. The patentable scope of the invention is definedby the claims, and may include other examples that occur to thoseskilled in the art. Such other examples are intended to be within thescope of the claims if they have structural elements that do not differfrom the literal language of the claims, or if they include equivalentstructural elements with insubstantial differences from the literallanguages of the claims.

It will be understood that the particular embodiments described hereinare shown by way of illustration and not as limitations of theinvention. The principal features of this invention may be employed invarious embodiments without departing from the scope of the invention.Those of ordinary skill in the art will recognize numerous equivalentsto the specific procedures described herein. Such equivalents areconsidered to be within the scope of this invention and are covered bythe claims.

All of the compositions and/or methods disclosed and claimed herein maybe made and/or executed without undue experimentation in light of thepresent disclosure. While the compositions and methods of this inventionhave been described in terms of the embodiments included herein, it willbe apparent to those of ordinary skill in the art that variations may beapplied to the compositions and/or methods and in the steps or in thesequence of steps of the method described herein without departing fromthe concept, spirit, and scope of the invention. All such similarsubstitutes and modifications apparent to those skilled in the art aredeemed to be within the spirit, scope, and concept of the invention asdefined by the appended claims.

Thus, although there have been described particular embodiments of thepresent invention of a new and useful BIDIRECTIONAL POWER CONVERTER itis not intended that such references be construed as limitations uponthe scope of this invention except as set forth in the following claims.

What is claimed is:
 1. A bidirectional power converter operable toprovide alternating current (AC) power at an AC terminal of thebidirectional power converter in a transmit mode of the bidirectionalpower converter and provide direct current (DC) power at a DC outputterminal of the bidirectional power converter in a receive mode, saidbidirectional power converter comprising: an oscillator configured toprovide a drive signal at a base frequency when the bidirectional powerconverter is operating in the transmit mode; an amplifier configured toreceive power from a power source via a DC input terminal of thebidirectional power converter and provide an AC output signal to the ACterminal of the bidirectional power converter in response to receivingthe drive signal when the bidirectional power converter is operating inthe transmit mode; a modulator configured to selectively provide thedrive signal from the oscillator to the amplifier as a function of ahysteretic control signal when the bidirectional power converter isoperating in the transmit mode; a hysteretic receiver circuit configuredto receive a transmitted control signal at the bidirectional powerconverter and provide the hysteretic control signal to the modulator asa function of the received, transmitted control signal when thebidirectional power converter is operating in the transmit mode; atransmit relay configured to electrically connect the amplifier to theAC terminal of the bidirectional power converter when the bidirectionalpower converter is operating in the transmit mode and electricallydisconnect the amplifier from the AC terminal of the bidirectional powerconverter when the bidirectional power converter is operating in thereceive mode; a rectifier configured to receive an alternating currentpower signal from the AC terminal of the bidirectional power converterand provide a DC output to the DC output terminal of the bidirectionalpower converter when the bidirectional power converter is operating inthe receive mode; a receive relay configured to enable the rectifier toprovide the DC output to the DC output terminal of the bidirectionalpower converter when the bidirectional power converter is operating inthe receive mode and prevent the rectifier from providing the DC outputto the DC output terminal when the bidirectional power converter isoperating in the transmit mode; and a hysteretic control circuitconfigured to monitor the DC output and transmit a control signal as afunction of the monitored DC output when the bidirectional powerconverter is operating in the receive mode.
 2. The bidirectional powerconverter of claim 1, further comprising a direction control inputconfigured to receive a direction control signal, wherein the directioncontrol signal is provided to the transmit relay and the receive relayto set the bidirectional power converter in either the transmit mode orthe receive mode.
 3. The bidirectional power converter of claim 1,wherein the hysteretic control circuit comprises: a hystereticcontroller configured to provide a logic signal, wherein the logicsignal is a first binary value when a voltage of the DC output is lessthan a predetermined threshold and the logic signal is a second binaryvalue when the voltage of the DC output is more than the predeterminedthreshold and wherein the first binary value is different than thesecond binary value; and a coil pulse driver configured to receive thelogic signal and generate a magnetic field via a magnetic coupling coil,wherein the generated magnetic field is indicative of the logic signal;and the hysteretic receiver circuit comprises a magnetic sensorconfigured to receive a magnetic field and provide the hystereticcontrol signal to the modulator as a function of the received magneticfield.
 4. The bidirectional power converter of claim 1, wherein thehysteretic control circuit comprises: a hysteretic controller configuredto provide a logic signal, wherein the logic signal is a first binaryvalue when a voltage of the DC output is less than a predeterminedthreshold and the logic signal is a second binary value when the voltageof the DC output is more than the predetermined threshold and whereinthe first binary value is different than the second binary value; and aradio frequency (RF) transmitter configured to receive the logic signaland transmit an RF signal via an antenna, wherein the transmitted RFsignal is indicative of the logic signal; and the hysteretic receivercircuit comprises an RF receiver configured to receive an RF signal andprovide the hysteretic control signal to the modulator as a function ofthe received RF signal.
 5. The bidirectional power converter of claim 1,wherein the hysteretic control circuit comprises: a hystereticcontroller configured to provide a logic signal, wherein the logicsignal is a first binary value when a voltage of the DC output is lessthan a predetermined threshold and the logic signal is a second binaryvalue when the voltage of the DC output is more than the predeterminedthreshold and wherein the first binary value is different than thesecond binary value; and an optical transmitter configured to receivethe logic signal and transmit an optical signal via an infrared (IR)emitter, wherein the transmitted optical signal is indicative of thelogic signal; and the hysteretic receiver circuit comprises an IRreceiver configured to receive an optical signal and provide thehysteretic control signal to the modulator as a function of the receivedoptical signal.
 6. The bidirectional power converter of claim 1, furthercomprising: a coil connected to the AC terminal of bidirectional powerconverter, wherein the coil is configured to: receive the AC outputsignal from the amplifier and emit a corresponding electromagnetic fieldwhen the bidirectional power converter is operating in the transmitmode; and convert electromagnetic flux into an AC power signal when thebidirectional power converter is operating in the receive mode.
 7. Thebidirectional power converter of claim 6, wherein the coil comprises: awire coil, and a tuning capacitor connecting the wire coil to the ACterminal of the bidirectional power converter.
 8. The bidirectionalpower converter of claim 1, wherein the receive relay is configured to:enable the rectifier to provide the DC output to the DC output terminalwhen the bidirectional power converter is operating in the receive modeby electrically connecting the rectifier to the DC output terminal ofthe bidirectional power converter when the bidirectional power converteris operating in the receive mode; and prevent the rectifier fromproviding the DC output to the DC output terminal when the bidirectionalpower converter is operating in the transmit mode by electricallydisconnecting the rectifier from the AC terminal of the bidirectionalpower converter when the bidirectional power converter is operating inthe transmit mode.
 9. The bidirectional power converter of claim 1,further comprising: a DC charge control relay comprising a unified DCterminal, wherein the DC control relay is configured to: connect to theDC input terminal and the DC output terminal; electrically isolate theDC input terminal from the DC output terminal; electrically connect theDC input terminal to the unified DC terminal when the bidirectionalpower converter is operating in the transmit mode; and electricallyconnect the DC output terminal to the unified DC terminal when thebidirectional power converter is operating in the receive mode.
 10. Thebidirectional power converter of claim 1, wherein the modulator is anamplitude shift keyed modulator.
 11. The bidirectional power converterof claim 1, wherein the amplifier is a full bridge amplifier.
 12. Thebidirectional power converter of claim 1, wherein the rectifier is afull wave rectifier.
 13. The bidirectional power converter of claim 1,wherein the base frequency of the oscillator is approximately 100 kHz.14. The bidirectional power converter of claim 1, further comprising: aslow start circuit configured to provide a pulse width modulated signalthat increases from zero to one hundred percent duty cycle beginningwhen the bidirectional power converter begins operating in the transmitmode, wherein the rate of increase is generally linear; and a one shottimer configured to provide a one shot signal to the modulator when thebidirectional power converter begins operating in the transmit mode andfor a predetermined period of time thereafter, wherein: the modulator isfurther configured to provide the drive signal from the oscillator tothe amplifier when the pulse width modulated signal is on and at leastone of the hysteretic control signal and one shot signal are on.
 15. Thebidirectional power converter of claim 1, further comprising: aswitching regulator configured to generate bias voltages when thebidirectional power converter is receiving power from the power sourceat the DC input terminal of the bidirectional power converter, whereinthe switching regulator provides at least one of the generated biasvoltages to: the oscillator, the amplifier, the modulator, thehysteretic receiver circuit, and the transmit relay, and a slow startcircuit, a one shot timer, and a temperature sensor of the bidirectionalpower converter.
 16. The bidirectional power converter of claim 1,further comprising: a temperature sensor configured to monitor atemperature of the amplifier and provide a temperature sensing signal;and a control logic configured to provide a modulator enable signal tothe modulator as a function of the temperature sensing signal and adirection control signal such that the modulator enable signal isprovided when the direction control signal sets the bidirectional powerconverter in the transmit mode and the temperature sensing signal isindicative of a temperature less than a predetermined temperature,wherein the modulator does not provide the drive signal from theoscillator to the amplifier when the modulator is not receiving themodulator enable signal.
 17. The bidirectional power converter of claim1, further comprising: a linear regulator configured to receive the DCoutput from the rectifier and provide bias voltages to the hystereticcontrol circuit when the bidirectional power converter is operating inthe receive mode.
 18. The bidirectional power converter of claim 1,further comprising: a DC filter configured to smooth the DC outputprovided by the rectifier to the DC output terminal.
 19. Thebidirectional power converter of claim 1, further comprising: aplurality of isolators configured to isolate the DC input terminal fromthe AC terminal and the AC terminal from the DC output terminal of thebidirectional power converter such that the bidirectional powerconverter is an isolated power source in both the transmit mode and thereceive mode.